Monday, January 17, 2011

Boreus coloradensis

There aren't many insects out and about during the last week of the year - at least not in North America. A little later on you can find small black stoneflies on the snow near mountain streams. A few spiders or midges might also be out. With persistence you might even find a wingless cankerworm or two but December is not known as the best time of the year to look for bugs. Of course you can easily find over-wintering beetles, caterpillars and bugs under rocks and logs but as far as active insects go, your chances are limited. Unless, that is, you're lucky enough to find a scorpionfly. Not any scorpionfly, mind you, but a small black scorpionfly that shows up on the snow much like a tiny piece of dislodged bark or a perhaps a chipped piece of stone. We happened to be just lucky enough a few weeks ago to find some.

These first two images are of small (3-5 mm long) snow scorpionflies of the family Boreidae. They don't look much like other scorpionflies that have colorful wings and lighter-colored bodies but the long rostrum is a bit of a giveaway. The first picture is of a female with her long ovipositor. The second picture is of a male. Erik, Michael and I found these over Christmas break in Rock Canyon above Provo (Utah). It was a bit of an overcast day but once we got into the canyon, the air cleared out and the snow was beautiful. Finding the boreids was a real bonus.

There aren't that many scorpionflies around to begin with - just over 500 species worldwide. Of these only about 30 belong to the family Boreidae, or the snow scorpionflies. Norm Penny is the leading authority on these remarkable insects. His world catalogue indicates that the only species known from Utah is B. coloradensis - so that's what I'm calling these individuals, at least for now. I was a bit surprised to discover that the little creatures can jump. They can't project themselves as far as fleas (which seem to be relatives of the Mecoptera) but they did manage to jump several inches when I approached them. That's a long jump for a creature with legs that are not much bigger than the commas on this page. And to imagine that all this activity (limited though it may be) is managed on a blanket of ice crystals.

I was surprised to find that John Acorn also has a nice image of another species (I think) on the last page of the American Entomologist (Winter 2010). I'm guessing that he found it in Canada but you'll have to ask him.


Anonymous said...

Very nice.

Perhaps it's just a coincidence, but in size, appearance, habit, and behavior, these things almost seem to mimic snow springtails. I hope I can encounter these someday.

Sam Wells said...

Good point. Now that you mention it, I have seen springtails out in the winter occasionally.